Windows XP SP3 upgrade spells trouble for IE

Windows XP users who install the operating system's third service pack will not be able to roll back their versions of Internet Explorer, Microsoft's deployment manager for Internet Explorer 8 has warned.

Writing on the MSDN website, Jane Maliouta said people who are trying out Internet Explorer 7 (IE7) and want to roll back to IE6 would need to complete that downgrade before installing XP Service Pack 3 (SP3), otherwise that option would be impossible in future. The same applies to those trialling the beta version of IE8 with a view to using IE7 or IE6 in future.

"If you are currently running IE7 on XP SP2, Windows Update will offer you XP SP3 as a high-priority update," wrote Maliouta on Monday. "If you choose to install XP SP3, IE7 will remain on your system after the install is complete. Your preferences will be retained. However, you will no longer be able to uninstall IE7."

Maliouta went on to claim that the decision to prevent these sorts of downgrades was "by design".

"When we install IE7 on Windows XP SP2, we back up the existing IE6 files in an uninstall directory," Maliouta wrote. "Those IE6 files are the ones that shipped on XP SP2, plus all the security updates you've installed while using IE6. Windows XP SP3 contains a newer version of the IE6 files. If you have XP SP3 on your system and uninstall IE7, your system would revert to the backed-up (older) version of the IE6 files, rather than the newer XP SP3 version."

"You would end up in a mixed file state in Windows, where most files would be the upgraded XP SP3, except for the IE6 files restored when uninstalling IE7. This state is not supported and is very bug prone. To ensure a reliable user experience, we prevent this broken state by disabling the ability to uninstall IE7."

In the case of those trying out IE8 Beta 1 on XP SP2, XP SP3 will not be offered via Windows Update. Maliouta said this was to dissuade users from finding themselves locked into a beta form of the browser, because the "remove" option would be unavailable after upgrading to XP SP3.

"Since people are more likely to uninstall beta software, we strongly recommend uninstalling IE8 Beta 1 prior to upgrading to Windows XP SP3, to eliminate any deployment issues, and installing IE8 Beta 1 after XP SP3 is on your machine," Maliouta added.